As a sensor board used for an exhaust gas sensor or the like, there is employed a sensor board including an insulating substrate formed of a ceramic sintered compact such as an aluminum oxide sintered body, and a detecting electrode disposed on a surface of the insulating substrate. For example, in association with adhesion of a to-be-detected substance contained in the exhaust gas to the detecting electrode, change in the resistance or the current value of the detecting electrode is caused by a decrease in the electric insulation relative to adjacent another detecting electrode. Thus, on the basis of this change in the resistance or the current value, the content of the to-be-detected substance in the exhaust gas or the like is calculated and detected.
As the material used for forming the detecting electrode, platinum is widely employed which is a metallic material less prone to be oxidized even at a high temperature of the exhaust gas or the like.